timepiece vs sundial

timepiece and sundial both are nouns.

Word	Noun	Adjective	Verb	Adverb
timepiece	Yes	No	No	No
sundial	Yes	No	No	No

As nouns, sundial is a hyponym of timepiece; that is, sundial is a word with a more specific, narrower meaning than timepiece:

timepiece: a measuring instrument or device for keeping time
sundial: timepiece that indicates the daylight hours by the shadow that the gnomon casts on a calibrated dial

Other hyponyms of timepiece include atomic clock, clock, sandglass, timer, ticker, watch.

timepiece (noun)	sundial (noun)
a measuring instrument or device for keeping time	timepiece that indicates the daylight hours by the shadow that the gnomon casts on a calibrated dial